Polycarbonate resins are used as a raw material in various fields including optical materials such as optical films, optical disks and lenses and housings such as electric appliances, and polycarbonate resins which are more excellent in performances are desired to be developed as the application fields are expanded.
On the other hand, in recent years, proposed as an electrophotographic photoreceptor in which a photosensitive layer is provided on a conductive substrate are an organic electrophotographic photoreceptor (OPC) of a laminate type having two layers of a charge generating layer (CGL) which generates a charge as a photosensitive layer at least by exposure and a charge transporting layer (CTL) which transports a charge and an organic electrophotographic photoreceptor of a single layer type in which a photosensitive layer comprises a single layer containing a charge generating material and a charge transporting material each dispersed in a binder resin or a single layer containing only a charge generating material dispersed in a binder resin, and they are used. Further, in order to improve a durability of an electrophotographic photoreceptor and enhance an image quality, put into actual use is OPC in which polytetrafluoroethylene fine particles are dispersed in a photosensitive layer or in which an overcoat layer is provided on an uppermost layer of a photosensitive layer (refer to, for example, a Non-Patent Document 1).
The above organic electrophotographic photoreceptor is required to be provided with a prescribed sensitivity, electric characteristics and optical characteristics according to electrophotographic processes applied. In the above organic electrophotographic photoreceptor, the surface of the photosensitive layer is subjected repeatedly to operations such as corona charge or contact charge using a roll and a brush, toner development, transfer onto paper and cleaning treatment, and therefore electric and mechanical external forces are exerted every timer the above operations are carried out. Accordingly, a durability against the above external forces are requested to a photosensitive layer provided on the surface of an electrophotographic photoreceptor in order to maintain an image quality of electrographs over a long period of time. To be specific, required is a durability against generation of abrasion and scratches on the surface caused by friction, corona charge and contact charge and deterioration of the surface caused by active gas such as ozone in transferring.
In order to meet the above requirements, polycarbonate resins having a good compatibility with a charge transporting material used for a photosensitive layer and good optical characteristics have been used as a binder resin for an organic electrophotographic photoreceptor. That is, polycarbonate resins in which 2,2-bis(4-hydroxyphenyl)propane (bisphenol A) and 1,1-bis(4-hydroxyphenyl)cyclohexane (bisphenol Z) are used as raw materials have been used as the above polycarbonate resins. However, even the above polycarbonate resins in which the above bisphenol A and bisphenol Z are used as raw materials are unsatisfactory for satisfying the requirements described above.
Electrophotographic photoreceptors containing a polycarbonate resin copolymerized with siloxane are investigated as means for solving the problems described above (refer to, for example, Patent Documents 1, 2 and 3). However, the copolymers disclosed in the above documents are combined via a chemically instable Si—O—C bond and therefore involve problems on deterioration of mechanical characteristics caused by cutting of molecular chains and degradation of charging characteristics brought about by a silanol group remaining at a molecular end. In order to solve the above problems, copolymerized polycarbonate resins combined via a chemically stable Si—C bond are proposed (refer to, for example, Patent Documents 4 and 5). Photoreceptors using the above polycarbonate resins have a low surface energy and therefore are improved in a cleaning characteristic, but they do not necessarily have a satisfactory effect of improving an abrasion resistance.    [Non-Patent Document 1]: No. 3 Japan Image Academy, Lecture Abstract of Technical Courses, p. 91    [Patent Document 1]: Japanese Patent Application Laid-Open No. 132954/1986    [Patent Document 2]: Japanese Patent Application Laid-Open No. 240655/1990    [Patent Document 3]: U.S. Pat. No. 2,989,251    [Patent Document 4]: Japanese Patent Application Laid-Open No. 72753/1993    [Patent Document 5]: Japanese Patent Application Laid-Open No. 232503/1998